Ecological patterns of body-size and clutch-size variation in the parthenogenetic teiid lizard Cnemidophorus tesselatus

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Pattern class C of parthenogenetic Cnemidophorus tesselatus reaches its southern range limit at Sumner Lake State Park, De Baca County, New Mexico, where it is syntopic at several sites with a northern population of pattern class E of the same species. Samples collected at Sumner Lake in 1997 confirmed significant differences between the two pattern classes in body length and clutch size initially observed in samples collected in 1995 and 1996. In contrast, these characteristics were non-significantly different in pattern classes C and Colorado D, sympatric (and marginally syntopic) at sites near the historic town-site of Higbee, Otero County, Colorado. The difference between each pair of sympatric pattern classes is based on different mean body sizes and a positive relationship between clutch size and body size in C. tesselatus. A comparison of 10 samples of three color pattern classes of C. tesselatus, spanning approximately 1100 km of latitudinal range, revealed that the small clutch size characterizing pattern class E at Sumner Lake was found in other populations of pattern class E and in one population of pattern class C as well. Similarly, the larger clutch size of pattern class C at Sumner Lake was found in the Higbee population of pattern class C and in some populations of pattern class E. Therefore, despite constraints on variability predicted from a parthenogenetic reproductive mode, reproductive characteristics are remarkably variable both within and between pattern classes. In the absence of conclusive evidence of more than one hybridization event in the origin of C. tesselatus and the geographic proximity of only pattern class E to the progenitor species, we hypothesize, from color pattern and meristic evidence, that pattern class C was most likely derived from one or more E-like individuals, and that pattern classes New Mexico D and Colorado D were derived from individuals of pattern class C. Mutations could also have modified reproductive characteristics permitting C. tesselatus to expand its distribution beyond that available to a general-purpose genotype derived from the progenitor species C. tigris marmoratus and C. gularis septemvittatus and expressed in pattern class E. In addition to its extensive geographic range, the ecological success of C. tesselatus can be gauged by the fact that nine of our 10 samples of C. tesselatus were from populations sympatric with 1-3 sexual species and 1-2 parthenogenetic species of Cnemidophorus.

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